Fine-tuning bromide AIE probes for Hg2+ detection in mitochondria with wash-free staining
Tian Tan, Chuang Zhang, Ying Han, Ruijun Chu, Wenyu Xi, Xulang Chen, Jingyu Sun, Hong Huang, Yan‐Jun Hu, Xiaohuan Huang
Abstract
Mercury ions (Hg 2+ ) primarily target mitochondria in the cells. Therefore, the development of novel probes that specifically target mitochondria in the presence of Hg 2+ is of immense importance. Most previously reported probes that utilize the softness of S, Te, O, and/or N atoms for Hg 2+ binding often face problems such as fluorescence quenching and off-target signals. In this study, bromide-hydrocarbon pyridinium salts were designed to target the mitochondria and chelate Hg 2+ via Hg–Br coordination bonds. As a prototype, four aggregation-induced emission (AIE) fluorogens , namely TPP-Br , TPP-Cl , R1 , and R2 , with a similar D-π-A structure but slight differences in their halogen substituents, were designed. Among them, only TPP-Br achieved the highly selective and sensitive detection of Hg 2+ by triggering its AIE properties, resulting in remarkable emission enhancement (80-fold), colorimetry , and the Tyndall effect. TPP-Br exhibited high selectivity and sensitivity to Hg 2+ with a detection limit of 0.35 μM, rapid response time (<10 s), and large Stokes shift of 185 nm. Their interaction modes were studied using a combination of 1 H nuclear magnetic resonance spectroscopy , scanning electron microscopy, fluorescent lifetime decay, and theoretical calculations. TPP-Br exhibited a low emission background in cells, whereas in the presence of Hg 2+ , mitochondria were lit up with wash-free staining. This study provides a powerful tool for accurately diagnosing mercury poisoning–related diseases in mitochondria.